| 摘要 |
PURPOSE:To constitute a filter which has complicate characteristics over a wide range by composing the filter of a delay element, a weighting multiplier, and an adder and setting the unit delay time of the delay element equivalently to an integral multiple of the sampling time interval of an input signal. CONSTITUTION:The unit delay time is set to 1/f02<-4>sec to fix the coefficient of an FIR (finite impulse response) type filter, and a clock frequency is set to f0Hz for an actual input signal which has a sampling interval 1/f0sec. Then, the delay time nT per stage of the delay element S4-1 of a digital filter S4 is set to 1/f02<-4>sec. The output of S4 is inputted to a digital filter F4 with low- pass characteristics whose delay time per delay element is 1/f02<-3>sec so as to erase even-numbered pass bands. The output of F4 is added by an adding circuit D4 to the output of a digital filter S3 with band-pass characteristics whose delay time per delay element is 1/f02<-3>sec. Similarly, the same process is repeated to obtain an output having target characteristics form a final digital filter F0.
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